Elevator control system



Feb. 26, 1952 PINTO 2,586,859

ELEVATOR CONTROL SYSTEM- Fi-ld Jan. 3, 1949 4 Sheets-Sheet l UB DB FIQI INVENTOR BY 'm'mv 1 11' ATTODNEY Feb. 26, 1952 A. PINTO 2,586,859

ELEVATOR CONTROL SYSTEM Filed Jan. 5, 1949 4 Sheets-Sheet 2 t-o. l

5GB I B 50B 2% ZUB IUB RNT U2 ZUFI IUFI x ULPB x us

HG 2 W PQ$ INVENTOR BY W ATTORN EY Patented Feb. 26, 1952 ELEVATOR CONTROL SYSTEM Anthony Pinto, New Rochelle, N. Y., assignor to Otis Elevator Company, New York, N. Y., a corporation of New Jersey Application January 3, 1949, Serial No. 69,022

7 Claims.

The invention relates to control systems for elevators.

There is considerable advantage in elevator installations in utilizing a direct current hoisting motor supplied with current from a variable voltage direct current generator. There is also advantage in providing levelling mechanism to bring the car to an exact landing level in making stops at the landings. The hoistway door and car gate (where provided) are operated either manually or by power mechanism, or by a combination of the two.

There is considerable savin in time in effecting the opening of the hoistway door and/or car gate during the levelling operation, or during slow speed operation when levelling mechanism is not provided. It is important that the car be prevented from running above a certain slow speed once the door and/or gate have started to open. This obviates any danger to passengers which might otherwise result from a sudden increase in car speed as they are about to step into or out of the car.

The object of the invention is to provide, for an elevator system in which a direct current hoisting motor is supplied with current by a variable voltage direct current generator, a simple and reliable control of the generator excitation for the slow speed operation which insures that the car can not operate above that speed at that time.

While the invention will be described as applied to a system in Which the car is under the control of the passengers themselves and in which self-levelling mechanism is employed for causing the car to be brought to an exact landing level in stopping, it is to be understood that the invention is applicable to other elevator systems, whether provided with self-levelling mechanism or not, such as those in which the car is under the control of an attendant, or under the control of passengers and an attendant.

The invention involves utilizing the same generator field winding for providing the generator excitation for all operating speeds, with the field winding excited from a relatively high voltage source for full speed operation and from a relatively low voltage source for slow speed operation. For full speed operation, the field winding may be self excited or excited from a separate source of current. It is usual in installations of this character that the generator be driven by a polyphase induction motor supplied with current from a polyphase alternating current source. According to the preferred arrangement,

for slow speed operation, the generator field winding is supplied with rectified current from a low voltage transformer which may be excited from the alternating current source which supplies the current for the generator driving motor. Where the generator field winding is self excited for full speed operation, the low voltage rectifier source may also be employed to establish the generator polarity for starting.

In the drawings:

Figure 1 is a simplified schematic representation of an elevator installation to which the invention is applicable;

Figures 2 and 3 constitute a simplified Wiring diagram in across-the-line form of an elevator control system chosen to illustrate the invention and suitable for the installation of Figure 1;

Figure 4 is a view similar to Figure 3 of a modified arrangement of certain of the generator circuits; and

Figures 28, 3S and 48 are spindle diagrams for Figures 2, 3 and 4 respectively showing the electromagnetic switches in spindle form with the contacts and coils arranged on the spindles in horizontal alignment with the corresponding contacts and coils in the wirin diagrams.

For a general understanding of the invention, reference may be had to Figure 1. The elevator car I0 is raised and lowered by means of the hoisting motor M, which drives a traction sheave l2 over which pass hoisting ropes I3 for the car and counterweight M. An electromechanical brake BR is provided and is applied in stopping the car and holding the car when at rest. Current is supplied to the hoisting motor by the generator G of a motor generator set. GM is the driving motor for the generator.

For illustratin the principles of the invention, a type of elevator control system has been illustrated which is known as collective control. The pressing of a push button either in the car or at a landing starts the car in a direction toward the floor for which the push button is provided. The car is slowed down and stopped at landings for which push buttons have been pressed, the car being automatically restarted after each stop so long as push buttons remain to be responded to.

An installation of only three floors is illustrated. A push button CB is provided in the car for each of the floors. Also an up push button U8 and a down push button DB are provided at the second floor, a push button is provided at the first floor which will be considered an up button and designated UB and a push button is provided at the third floor which will be considered a down button and designated DE. The push buttons act through floor relays to register calls. The push buttons in the car will hereinafter be termed car buttons while those at the floors will hereinafter be termed landing buttons.

Mechanism actuated in accordance with car movement is utilized, this mechanism being diagrammatically illustrated as a floor selector. This floor selector designated 20 is driven preferably by means of a tape 2i extending from the car to the counterweight and having teeth thereon for engaging teeth on the selector driving wheel 22. It comprises a crosshead 23 which is driven by a screw 24. This screw is driven through beveled gears 25 by the shaft 26 on which the driving wheel is mounted, thus moving the crosshead in accordance with movement of the car. The crosshead carries mechanism for controlling the direction of car travel and mechanism for controlling the picking up and cancelling of the calls. Mechanism is also provided on the floor selector for causing slow down and stopping of the car.

The levelling mechanism is illustrated as of the inductor type and comprises an up levelling switch LU and a down levelling switch LD, both carried by the car. The switches are operated by stationary inductor plates 30, one at each floor. Also carried by the car and arranged between switches LU and LD for operation by the inductor plates is a door zone switch DZ.

Door operating mechanism is illustrated. It is of the type which operates both the car gate and hoistway doors. This mechanism comprises an operating motor DM carried by the elevator car. This motor acts through a crank wheel 3| and chain 32 to operate a lever 33 pivoted on the car and connected by a link to the car gate 34 to open the gate. This lever is biased by a spring 35 to gate closed position. A cam plate 36 carried by the car gate passes between rollers 37 on the hoistway door (not shown) as the car arrives at the floor and acts therethrough to unlock and open the door as the gate is opened, and also to close and lock the door as the gate is closed.

Reference may now be had to Figures 2 and 3. The control system is a variable voltage control system and is illustrated as considerably simplified as compared with control systems utilized in commercial installations. It is to be understood that in applying the invention to control systems used commercially many changes may be made, especially in adapting the invention to the more comprehensive circuits and to control features and apparatus not here shown. The circuits of Figure 3 are principally the generator field winding and armature circuits. The remainder of the circuits including the control circuits are illustrated in Figure 2.

The elevator hoisting motor, designated M in Figure 1, is a direct current motor having an armature MA and a separately excited field winding MF. The motor armature is supplied with current from the armature GA of the variable voltage direct current generator G of Figure l, The generator has two field windings, a series field winding GSF and a shunt field winding SHF. The driving motor GM of Figure l for the generator is a three phase squirrel cage induction motor. The stator windings of this motor are designated GMSI, GMSZ and GMS3 and its rotor GMR. I, II and III are the alternating current supply lines for the generator driving motor. Also, the door operating motor DM is illustrated as a three phase squirrel cage induction motor which is supplied with current from the supply lines I, II and III. The stator windings of the door operating motor are designated DMSI, DMSZ and DMS3 and its rotor is designated DMR. Current for the coils of electromagnetic control switches is derived from the alternating current supply lines. In the system illustrated a rectifier SR5 is interposed between the supply lines and the switches to permit direct current switches to be employed. A transformer TRFI is interposed between the rectifier and the supply lines to obtain the desired operating voltage for the switches.

The generator shunt field winding SHF is arranged for excitation from the generator armature as a self excited field winding for full speed operation. For establishing generator polarity in starting and for the levelling operation, the generator shunt field winding is excited from a low voltage source. This source comprises a step-down transformer TRFQ having its secondary winding connected to rectifiers SRl SR2, SR3 and SR4 arranged in bridge formation. The primary winding of transformer TRF2 is connected to alternating current supply lines II and III, the connecting lines extending from Figure 2 to Figure 3.

The letters UB, DB and CB, designating the landing buttons and car buttons, are preceded by numerals indicating the floors for which the buttons are provided. The push buttons act through floor relays designated first by the numeral corresponding to the floor for which the relay is provided and then by the letters CF, UF or DF in accordance with whether the floor relay is for a car button, an up landing button or a down landing button. Each of the floor relays is provided with an operating coil and a release coil. The floor relay when operated is latched in operated condition thereby registering the call. When the call is answered, the release coil is energized to release the latch, thereby cancelling the call.

The picking up and. cancelling of the calls is effected through brushes carried by the crosshead of the floor selector and coperating stationary contacts. There is a stationary contact for each of the car buttons, these contacts being arranged on the floor selector in a vertical column in accordance with the floors for which they are provided and being subject to contacts of the car button floor relays for the corresponding floors. These contacts, designated CS preceded by a numeral corresponding to the floor for which the contact is provided, are adapted to be engaged by the up car call pick up brush UCPB, the down car call pick up brush DCPB and the car call cancelling brush CCB. There is a stationary contact for each of the down landing buttons, these contacts also being arranged in a vertical column in accordance with the floors for which they are provided and being subject to the contacts for the down landing button floor relays for the corresponding floors. These contacts, designated DS preceded by the numeral corresponding to the floor for which the contact is provided, are adapted to be engaged by the down landing call pick up brush DLPB and down landing call cancelling brush DLCB. There is a stationary contact for each of the up landing buttons, these contacts also being arranged in a vertical column in accordance with the floors for which "they are provided and being subject to the contacts for the up landing button floor relays for the corresponding floors. These contacts, designated US preceded by the numeral corresponding to the floor for which the contact is provided, are adapted to be engaged by the up landing call pick up brush ULPB and up landing call cancelling brush 'ULCB. The call cancelling brushes are in engagement with their stationary contacts when the car is opposite the floor for which the stationary contacts are provided, whereas the call pick up brushes engage these contacts in advance of the arrival of the car in the direction for which the brush is provided.

The push buttons also act through their floor relays in cooperation with direction mechanism on the floor selector to control the direction of car travel. This direction mechanism comprises a plurality of hook switches HS, one for each floor, these hook switches being differentiated as to floors by numerals corresponding to the floors preceding the letters. The hook switches are arranged in a vertical column and are adapted to be engaged by a two section direction cam desi nated BBC. The lower section of this cam is of conducting material while the upper section is of insulating material.

Referring back to Figure 1, the floor selector slow down and stopping mechanism comprises pawls carried by the crosshead and biased to extended position for engaging stopping lugs positioned on upright members of the floor selector. There are two pawls one designated dl for up car travel and the other designated 42 for down car travel. Up stopping lugs 43 for engagement by the up pawl are provided for the second and third floors while down stopping lugs it for engagement by the down pawl are provided for the second and first floors. An electromagnet is provided for controlling the extension and retraction of the pawls. This magnet, which will hereinafter be termed pawl magnet and designated PM, is carried by the crosshead. The pawl magnet when energized retracts the pawls from the stopping lugs, resulting in the closing of selector.

switches SLSI, SLSZ and SLS3. When a call is picked up, the pawl magnet is deenergized, permitting the pawls to be extended for cooperation with the stopping lugs. As the crosshead continues its movement, the pawl for the direction of car travel engages the stopping lug for the floor for which the call has been picked up, causing the opening of selector switches SLSl, SLS2 and SLS3 in sequence which causes the car to be slowed down and brought to a stop at that floor.

Referring again to Figures 2 and 3, the electromagnetic control switches employed in the system illustrated are designated as follows:

D, down direction switch DC, door close switch DO, door open switch DR, door reopen switch IE, first slow down switch 2E, second slow down switch K, motor generator set starting switch MC, minimum current field relay .NT, time relay SS, stop switch U, up direction switch VR, voltage relay XD, down direction relay XU, up direction relay Throughout the description which follows, these designated switches. Also, with reference numerals appended thereto they will be applied to the contacts of these switches. The release coil of the electromechanical brake is similarly designated BR.

The circuits are shown in straight or acrossthe-line form in which the coils and contacts of the various switches are separated in such manner as to render the circuits as simple and direct as possible. The relationship of the coils and contacts may be seen from Figures 28 and 38 where the switches are arranged in alphabetical order and where the coils and contacts are positioned on spindles in horizontal alignment with the corresponding elements of the wiring diagram. The spindles of the switch-es appearing in Figure 3 are not aligned vertically in Figure 3S with the corresponding spindles of Figure 28, being brought together and placed beside Figure 3 to avoid a separate sheet of drawings. The brake coil BR and the coil PM of the pawl magnet are included on the spindle diagram of Figure 28. The levelling switches LU and LD and the door zone switch DZ are also included in Figure 2S. The electromagnetic switches are illustrated in deenergized condition, switch SS being of the latching type and being shown in reset condition.

The contacts operated by the car gate when it reaches closed position are designated GC. The hoistway door contacts are designated DCS. The circuits are arranged so that the car gate and hoistway door are closed and the hoistway door locked when the car is parked at a floor. Therefore contacts GC and DOS are engaged. ES is the emergency stop switch in the elevator car. IUSL and !DSL are respectively the first up slow down limit switch and the first down slow down limit switch and ZUSL and ZDSL are respectively the second up slow down limit switch and the second down slow down limit switch. UL and DL are respectively the up stop limit switch and down stop limit switch and FUL and FDL are respectively the final up limit switch and the final down limit switch. Resistances are designated generally by the letter R.

The circuits are illustrated for the condition with the car standing at the first floor. It will be assumed that the time interval of time relay NT has expired.

Assume now that an intending passenger at the second floor presses up second floor landing button ZUB. This causes the up second floor relay 2UP to latch in operated condition. Upon operating, this relay engages contacts 2UF2 which completes a circuit through contacts NTZ, resistance RU2, contacts ZFUZ, hook switches 2HS and 3H3, contacts XD2 and contacts D2 for the coil of up direction relay XU. Relay XU, upon operation, separates interlock contacts XUt. It also engages contacts XUI to complete a circuit for the coil of motor generator set starting switch K. Switch K, upon operation, engages contacts Kl, K2 and K3 which connects the stator windings of the generator driving motor to the supply lines to start the motor-generator set in operation.

Switch K also disengages contacts K4 to remove the short circuit for the coil of minimum current field relay MC. Relay MC engages contacts MCI to complete a circuit through limit switches FUL and FDL, contacts MCL, emergency switch ES, car gate contacts GO, contacts XU'I and contacts NT3 for the operating coil of stop switch SS. Switch SS operates to engage contacts SS2, completing a circuit for the coil of pawl magnet PM. The pawl magnet acts to retract the pawls, disengaging down pawl 42 (Figure 1) from the first floor stopping collar 44 with the result that the selector slow down and stop switches SLSI, SLSZ and SLS3 engage.

The engagement of selector switch SLS3 completes a circuit through limit switches FUL and FDL, contacts MCI, switch ES, car gate contacts GC, hoistway door contacts DCS in series relation, switch SLS3, contacts XU5, contacts D4 and limit switch UL for the coil of up direction switch U. Switch U, upon operation, separates interlock contacts U3 and U6 and engages contacts U2 to render brushes UCPB and ULPB alive for up car travel. It also engages contacts UI to complete a circuit for the coil of time relay NT. Relay NT, upon operation, separates contacts NT2 but without effect as they are by-passed by contacts XU2, separates contacts NT3 without effect as stop switch SS is latched in operated condition and engages contacts NT l without effect as contacts SS3 are now separated.

Switch U, upon operation, also engages contacts Ull to connect the primary winding of low voltage transformer TRFZ to alternating current supply lines II and III. Switch U also separates contacts U9 to disconnect the generator shunt field winding SI-IF from across the generator armature and engages contacts U10 and Ul2 to connect field winding SHF across the diagonal of the rectifier bridge to the secondary winding of transformer TRF2. This circuit for one half cycle of transformer secondary voltage is from the lower end of the secondary winding of transformer TRFZ through rectifier SR4, contacts Ul2, field winding SHF, contacts 2E4, contacts Ulfl, rectifier SRI to the upper end of the transformer secondary winding. For the other half cycle, the circuit is from the upper end of the secondary winding through rectifier SR2, contacts U12, field winding SHF, contacts 2E4, contacts UN] and rectifier SR3 to the lower end of the transformer secondary winding. Switch U also engages contacts U8 to complete a circuit for the brake release coil BR. This causes the brake to be released and, with the energization of field winding SHF, sufficient voltage is generated by the generator armature GA for application to motor armature MA to effect the start ing of the car. The direction of current flow in field winding SHF causes the polarity of the voltage generated to be such as to cause the car to start in the up direction.

Switch U, upon operation, also engages contacts U? which completes a circuit through switch lUSL, contacts U1 and switch SLSl for the coil of first slow down switch IE. Switch E, upon operation, engages contacts lEi to short circuit resistance RS. Switch U also engages contacts U5 which completes a circuit through switch ZUSL, contacts U5, switch SLSZ and contacts VRI for the coil of second slow down switch 2E, contacts VRI being engaged as a result of the completion of the circuit for the primary winding of transformer TRF'Z. Switch 2E, upon operation, separates contacts 2E2 to deenergize the coils of inductor levelling switches LU and LD and inductor door zone switch DZ. It also separates contacts 2E4 and engages contacts 2E3 to connect the generator shunt field winding for self excitation across the generator armature GA. This circuit is from the right hand side of the generator armature through series field winding GSF, contacts UH], rectifier SR1 (or SR3), secondary winding of transformer TRFZ, rectifier SR4 (or SR2), contacts Ul2, field winding SHF, contacts 2E3 and Hill to the left hand side of the generator armature. This circuit is through the transformer secondary winding which constitutes the main source of excitation for the generator shunt field, winding until the generator voltage starts to build up. As the generator voltage builds up the voltage applied to the coil of voltage relay VR decreases and this relay drops out. When this occurs switch 2E remains operated due to its self holding contact 2E]. The short circuit of resistance RS in circuit with the generator shunt field winding acts to cause the resistance line of the field winding to be of a slope such as will result in the generator voltage building up to a value to bring the motor to the desired full operating speed.

As the car approaches the second floor, brush ULPB engages second floor stationary contact 2US which completes a circuit through the release coil of stop switch SS, contacts U2, brush ULPB, contact 2US, contacts 2UFI and the release coil of the up second floor relay ZUF. The current which flows in this circuit is not sufficient to effect the release of the up second floor relay but the release coil of stop switch SS is energized sufficiently to release the latch, permitting this switch to drop out. At substantially the same time that brush ULPB engages contact US, the upper section of cam DRC engages and opens hook switch ZHS, breaking the circuit for the coil of up direction relay XU which drops out. Contacts U4 maintain the circuit for the coil of up direction switch U after contacts XUS separate. Upon dropping out switch SS separates contacts SS2 to deenergize the pawl magnet, thereby effecting the release of the pawls for cooperation with the stopping collars.

Upon continued upward movement of the car, up pawl 4| engages the second floor stop collar 43 which with further movement of the car effects the opening of selector switch SLSI. The opening of switch SLSI breaks the circuit for the coil of first slow down switch IE. Switch IE drops out, separating contacts IEI to remove the short circuit for resistance RS which increases the slope of the resistance line of the shunt field winding circuit. This results in the decrease of the voltage of the generator and thus in the speed of the car.

As the car arrives at a point still closer to the floor the up levelling inductor switch LU comes opposite the inductor plate for the second floor. Shortly thereafter selector switch SLS2 opens to break the circuit for the coil of second slow down switch 2E. Switch 2E upon dropping out separates contacts 2E3 and engages contacts 2E4 to disconnect the generator shunt field winding from across the generator armature and to cause the field Winding to be excited solely by the transform secondary winding. This causes further reduction in generator voltage and consequent further decrease in the speed of the elevator hoisting motor. Switch 2E also engages contacts 2E2 to complete the circuit for the coils of inductor levelling switches LU and LD and inductor door zone switch DZ. The energization of the coil of inductor switch LU, owing to the fact that this coil is now in the zone of the second floor plate, causes the engagement of contacts LUI to establish an additional circuit for the coil of up direction switch U.

As the car arrives at a point still closer to the second floor, selector switch SLS3 opens, transferring the control of the circuit for the coil 9 of up direction switch U to contacts LU! of the up levelling switch. As the car arrives at the second floor, up levelling inductor switch LU passes off the inductor plate permitting the separation of contacts LUI to break the circuit for the coil of up direction switch U. Switch U, upon dropping out, separates contacts Ulil and UlZ to discontinue excitation of the generator shunt field winding and separates contacts U8 to break the circuit for the brake release coil to apply the brake, bringing the car to a stop at the second floor. Switch U also engages contacts U9 to reconnect the generator shunt field winding SHF across the generator armature with reverse polarity so as to counteract the efiect of residual fiux of the generator field.

Shortly before the car arrives at the second floor door zone switch DZ comes opposite the inductor plate, causing the engagement of contacts DZ2 to complete a circuit through door open limit switch DOL, contacts DZZ, contacts NT4 and contacts SS3 for the coil of door open switch DO. This switch engages contacts DOI, D02 and D03 to complete a circuit for the stator windings DMSI, DMS2 and DMS3 of the door operating motor to effect the opening of the car gate and the unlocking and opening of the second floor hoistway door. As the door and gate reach open position the door open limit switch DOL opens to break the circuit for the coil of door open switch D which drops out-to deenergize the door operating motor. Thus the door and gate are opened as the car is being brought to a stop at the floor.

As the car arrives at the floor, brush ULCB engages contact 2US completing another circuit for the release coil of up second floor relay ZUF, this circuit extending through contacts DZI, the coil of door reopen switch DR and contacts XD5. This causes sufficient current to be supplied to this release coil to release the floor relay, thereby automatically cancelling the call. The coil of switch DR is momentarily energized but its circuit is immediately broken by the separation of contacts 2UFI as the floor relay is released.

Switch U, in dropping out, also separates contacts UH to disconnect the primary winding of transformer TRFZ from the alternating current supply lines. Switch U also separates contacts UI' to deenergize the coil of time relay NT which is delayed in dropping out by the discharge of condenser CNT. Upon dropping out relay NT separates contacts NTI to break the circuit for the coil of switch K. It also engages contacts NT5 which completes a circuit through door close limit switch DCL and contacts NT5 for the coil of door close switch DC. This switch engages contacts DCI, D02 and D03 to complete a circuit for the stator windings of the door operating motor DM to effect the closing of the car gate and hoistway door and the locking of the door as it reaches closed position. As the door and gate reach closed position the door close limit switch DCL opens to break the circuit for the coil of door close switch D0 which drops out to deenergize the door operating motor. Switch K does not drop out immediately the circuit for its coil is broken, being delayed by the discharge of condenser CK. Upon dropping out switch K separates contacts Kl, K2 and K3 to disconnect the stator windings of the generator driving motor from the supply lines to shut down the motor generator-set.

If, with the car parked at a floor above the first floor, a push button is pressed for a floor below the car, the operated floor relay establishes a circuit for the coil of down direction relay XD. This circuit, say with the car at the second H001 and a first floor button pushed, is through hook switch I HS and the lower section of cam DRC. Relay XD causes the operation of down direction switch D. Switch D completes a circuit from the secondary winding of transformer TRFZ for exciting the generator shunt field winding for down car travel. The circuit is from one end of the secondary winding through rectifier SR4 (or SR2), contacts Dill, contacts 2E4, field winding SHF, contacts Dl2, rectifier SRI (or SR3), to the other end of the secondary winding. It is believed that otherwise, the'operation of starting the car in the down direction will be understood from the description of starting the car in the up direction.

The car gate and hoistway door at the floor at which the car is parked may be opened by pressing either landing button for that floor. The pressing of the landing button causes operation of the corresponding floor relay, say floor relay IUF with the car at the first floor, which causes engagement of contacts IUFI to complete a circuit through contacts DZI, the coil of door reopen switch DR, contacts XD5, brush UCLB, contact IUS, contacts IUFI and release coil IUF. Switch DR operates to engage contacts DR2 which completes a circuit for the coil of door open switch D0 to open the door and gate. Switch DO also engages contacts D04 to establish a self holding circuit, inasmuch as switch DR drops out as soon as the intending passenger removes his finger from the button. Switch DR when operated also engages contacts DR! to reestablish the circuit for the coil of time relay NT to insure ample time for the passenger to enter the car before reclosing of the gate and door takes place.

Response is had to all calls that are registered. As regards calls registered on car button floor relays, these calls are answered as the car reaches the floors for which the relays are provided, regardless of the direction of car travel, brush UCPB being effective during up car travel and brush DCPB being effective during down car travel for cooperation with stationary contacts CS to pick up the calls. As regards calls registered on landing button floor relays, however, up landing calls are answered during up car travel as the car reaches the floors for which such calls are registered and down landing calls are answered during down car travel as the car reaches the floors for which such calls are registered, brush ULPB being effective for up car travel for cooperation with stationary contacts US and brush DLPB being effective for down car travel for cooperation. with stationary contacts DS. If the highest call is a down landing call, this call is answered during upward car travel. The opening of the hook switch for the floor for which such call is registered upon the engagement thereof by the upper section of cam DRC breaks the circuit for the coil of up direction relay XU and relay XU in turn engages contacts XU3 to complete a circuit for the release coil of stop switch SS, causing the car to be slowed down and brought to a stop at the floor. The down call is automatically cancelled as the car arrives at the floor owing to the fact that brush DLCB is rendered alive by engagement of contacts XUG. Similarly, if the lowest call is an up landing call this call is answered during down car travel. As the insulating space between the two sections of cam DRC runs onto the hook switch for the floor for which such call is registered, the circuit is broken for the coil of down direction relay XD and relay XD in turn engages contacts XD3 to complete a circuit for the release coil of stop switch SS, causing the car to be slowed down and brought to a stop at the floor. The up call is automatically cancelled as the car arrives at the floor owing to the fact that brush ULCB is rendered alive by the engagement of contacts XD5. The car is automatically started after each stop so long as calls remain to be responded to. The reclosure of the car gate and hoistway door closes car gate contacts GC and door contacts DCS. The engagement of contacts GC causes operation of stop switch SS to release the pawls and the consequent engagement of switch SLS3, together with the engagement of contacts GC' and DCS, completes .the circuit for the coil of the direction switchselected by the operated direction relay. The direction relays XU and XD act to maintain the car set for travel in the same direction after. each stop so long as calls in that direction from the carremain to be responded to at the timethe call is picked up. Contacts NTZ act upon the farthest stop in agivendirection to provide time for an entering passenger to press a car button for his desired destination and thus determine the direction of car travel. The level ling mechanism acts to bring the car to a stop at the landing level, should it underrun or overrun the floor. Contacts LUI control in the event of an underrun in the up direction or an overrun in the down direction and contacts LDI con trol in the event of an underrun in the down direction or an overrun in the up direction. It is believed that these operations will be understood in view of previous description.

The above described arrangement enables the car gate and hoistway door to be opened as the car is being brought to a stop without allowing the car to run above a slow speed as the opening of the gate and door is effected. The door zone switch is not effective until the car is well into the levelling zone and not until switch 2E drops out to disconnect field winding SHF from the generator armature and reestablish. the circuit for exciting the field winding from transformer TRFZ alone. As the secondary voltage of transformer TRF'Z is of a low value suitable for levelling, it is impossible for the car to operate above a slow speed while the door and gate are being opened.

The embodiment above described has the further advantage that it enables the generator to be self excited for acceleration and full speed running, the transformer-rectifier bridge network providing the excitation for starting and insurin the establishment of the proper generator armature polarity for the desired direction of operation of the car. Furthermore, there is the further advantage that but a single generator shunt field winding is employed. Also, a sin le set of direction switches is emploved for both full speed operation and the levelling operation. Also. the transformer-rectifier network is a simple and reliable source of low voltage ex citation. Relay VR insures that the connection of the shunt field winding to the generator armature in starting can not be effected unless transformer TRF2 is effective to establish the polarity of generator excitation. In addition, the rectifiers insure that the generator field winding can not be excited by self excitation of a polarity opposite to that dictated by the operated direction switch as they act to block the flow of current in.

12 the reverse direction. The circuits may be arranged so that the rectifiers act to cause the generator excitation to build down in the event of reverse polarity of the generator armature.

A resistance HT is illustrated in the circuit for the primary winding of transformer TRFZ. This resistance may be utilized for adjusting the voltage of the transformer secondary to the desired value. It may also be controlled to provide different voltage values as where two speed levelling is employed and as where it is desired to have a lower voltage for starting than for levelling. Other arrangements may be employed.

The transformer-rectifier network may be utilized in other arrangements to provide low voltage for excitation of the generator shunt field winding. For example, in Figure 4 an arrangement is illustrated in which the generator shunt field winding is arranged for connection to an exciter for full speed operation instead of to the generator armature. This figure is similar to Figure 3, being directed to the generator field winding and armature circuits. The control and other circuits may be as illustrated in Figure 2.

In the arrangement of Figure 4, the exciter armature is designated EX, its shunt field Winding ESHF and its series field winding ESF. The transfer of the generator shunt field winding circuit from the transformer to the exciter is eifected by contacts 2E3 and 2E4 of switch 2E. As switch 2E operates immediately the direction switch is operated, the car is started on the excitation provided by the exciter with the transformer excitation employed for the slow speed operation in stopping. With this arrangement, it would be preferred to time the operation of switch IE for acceleration, as by any suitable timing arrangement. Also as the generator voltage is not built up by self-excitation, relay VB, is not employed to control the initial energizing circuit of the coil of switch 2E.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said motor, said generator having a shunt field winding; means for energizing said field winding for full speed operation of said motor; a source of alternating current of low voltage; unidirectional current conducting means; and means for discontinuing energization of said field winding for full speed operation of said motor and for causing energization of said field winding from said low voltage source through said unidirectional current conducting means for slow speed oper ation of said motor.

2. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said motor, said generator having an armature and a shunt field winding; means for connectin said field winding to said generator armature for full speed operation of said motor; a source of alternating current; a transformer excited from said source and having a secondary voltage of low value; and means for discontinuing excitation of said field winding from said generator armature and for causing only unidirectional current derived from the secondary of said transformer to be supplied to said field winding for slow speed operation of said motor.

3. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said motor, said generator having an armature and a.

shunt field winding; a source of alternating current; a transformer excited from said source and of said motor; and means for disconnecting saidfield Winding from across said generator armature and for connecting said field Winding across only said transformer secondary winding through said? unidirectional current conducting means for slow] speed operation of said motor.

4. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said; motor, said generator having an armature and a shunt field winding; a source of alternating current; a single phase transformer excited from said source and having a secondary voltage of low value; a plurality of unidirectional current a conducting means arranged in a bridge connected to the transformer secondary winding; a circuit for connecting said field winding to one diagonal terminal of said bridge; means for connecting said field winding across the diagonal terminals of said bridge-connected unidirectional current" conducting means and said generator armature for full speed operation of said motor; and means,

for disconnecting said field winding from across,

said generator armature and for connecting said field winding across only said diagonal terminals-Q of said bridge-connected unidirectional current conducting means for slow speed operation of said motor.

5. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said motor, said generator having a shunt field winding; means for energizing said field winding for slow speed operation of said motor, said means comprising only a source of alternating current,

a single phase transformer excited from said source, a plurality of rectifiers connected bridge formation to the transformer secondary. winding, and a circuit for connecting said field winding across the diagonal of said bridge; and means to connect said shunt field winding across the armature of said generator and said bridgeconnected rectifiers for full speed operation of said motor, said last named means acting to disconnect said field winding from across said generator armature for slow speed operation of said motor.

6. In combination; a direct current elevator hoisting motor; a direct current generator for supplying current at a variable voltage to said motor, said generator having an armature and a shunt field winding; a source of alternating current; a transformer-rectifier bridge network for supplying low voltage unidirectional current derived from said source; and means for connecting said shunt field winding across said generator armature and said transformer-rectifier bridge network in series for full speed operation of said motor, and for disconnecting said shunt field winding from across said generator armature while maintaining its connection across said transformer-rectifier bridge network for slow speed operation of said motor.

7. In combination, a direct current elevator hoisting motor; a direct current generator to supply current at a variable voltage to said motor, said generator having an armature and a shunt field winding; a source of alternating current; unidirectional conducting means connected to said source and adapted to supply unidirectional current from said source to said field winding; relay transfer means to connect said field winding across said armature and said unidirectional current conducting means for full speed operation of said motor, and to connect said field winding to only said unidirectional conducting means for slow speed operation of said motor; and relay transfer means to reverse the connections between said shunt field and said unidirectional conducting means to reverse the direction of rotation of said motor.

ANTHONY PINTO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,654,987 Mittag Jan. 3, 1928 1,891,072 Tyrrell Dec. 13, 1932 2,238,611 'I'ittel Apr. 15, 1941 2,321,969 Bany June 15, 1943 2,421,645 Partington June 3, 1947 

